The present application is directed to devices and methods for forming a toner image within an image forming device and, more particularly, to devices and methods that selectively drive developer members to prevent unnecessary wear on the toner.
Color image forming devices contain two or more cartridges, each of which transfers a different color of toner to a media sheet as required to produce a full color copy of a toner image. One common image forming device includes four separate cartridges for each of yellow, magenta, cyan, and black colors. Image formation for each cartridge includes moving the toner from a reservoir to a developer roll, from the developer roll to a photoconductive member, and from the photoconductive member to either a media sheet or an intermediate member. The toner image from each cartridge are formed on the media sheet in an overlapping arrangement that ultimately forms the final composite toner image.
In many devices, each cartridge is driven during image formation, even when one or more colors are not being used for the specific print job. When the cartridge is driven, the developer roll forces toner through multiple compressive nips, even when the developer roll is not actually transferring toner. Repeatedly passing toner through the compressive nips inflicts some level of damage to the toner. Worn or damaged toner particles may fail to transfer or may transfer too readily to the photoconductive member. Thus, each time a given particle of toner passes through a nip, the likelihood of that particle responding to the image formation process decreases.
Devices and methods to reduce or eliminate undue wear on the toner would result in better overall efficiency of the image forming device. This in turn would increase the amount of toner available for transfer to the media sheets, and would decrease the amount of wasted toner.